This invention relates generally to commercial deep fryers and specifically to means for filtering the cooking fat therein and for cleaning the fryer of dislodged food particles.
Deep fat fryers in which a quantity of oil or fat is heated to pre-determined temperature for cooking foods suspended therein are well known in the art. It is also commonly known that the appearance and taste of foods prepared in such fryers is in large measure dependent upon the temperature and amount of fat absorbed by the food during cooking. A poor tasting or deteriorated fat adversely affects both the taste and appearance of foods cooked therein and is to be avoided.
Cooking fats break down and deteriorate for a variety of reasons, among which are cooking temperature, amount of air and moisture in the fat and the presence of so-called ""debris" or dislodged and/or burned food particles. Deep fryers are generally designed with the heating elements supported above the bottom of the vessel or pot to provide a "cooler" zone between the vessel bottom and the heating elements. Dislodged food particles dropping to the bottom don't burn as rapidly because of the lower temperature and thus deteriorate the fat more slowly. Despite this, it is still necessary to regularly clean deep fryers to remove food particles and other debris by passing the fat through a filter mechanism to remove the fatty acids and solids. The fatty acids are a product of fat breakdown and contribute to the above-mentioned deterioration in appearance and taste of foods cooked in the fat. Since the fat is heated to a high temperature for cooking, the cleaning process is dangerous as well as time consuming.
One technique in the prior art for filtering cooking fat is known as the Keating Nutroilator Process from Keating of Chicago, Inc. In it free fatty acids are removed by adsorption with the use of a silicon dioxide powder and any particulate matter or debris is removed by filtration. A portable filter tank is placed beneath the fryer drain and the heated fat drained into it. The filtered fat is pumped back to the fryer by means of a hose. With the fryer drain open, the operator "hoses down" the bottom of the cooking vessel with filtered fat to flush food particles and debris from the vessel to the filter tank. When the vessel is clean, the drain is closed and the vessel refilled with the filtered fat via the hose. Since fat is absorbed by food during cooking, any required make up fat may be added to the fryer at this time.
The above cleaning and filtering technique has been used for years with good success. It does however require operator skill to effect cleansing of debris from the bottom of the vessel.
The system described in U.S. Pat. No. 3,900,580 utilizes a separate heater apart from the cooking vessel for heating the cooking oil. The pot includes a recessed filter bowl with a crumb trap arrangement for directing crumbs to a crumb well which communicates with a conveyor for mechanically removing crumbs. The oil is circulated in a turbulent flow by a pair of nozzles located at the sides of the pot above the bottom to work crumbs toward the filter. Oil is circulated for temperature control and continuously filtered. The system is quite complex and obviously very expensive.